The present invention is directed to a friction control article having a pleasant and soft feel, high friction properties, and good performance in wet and dry conditions.
The development of enhanced grip and anti-slip surfaces typically centers around the materials and the surface topology of the article. Common materials include natural and synthetic rubbers, styrenic block co-polymers, latex, ethylene vinyl acetate, ethylene-propylene rubber, polyurethane, polyester co-polymers, polyimides, and the like. The surface topology can range from smooth to having exaggerated gripping structures.
U.S. Pat. No. 3,585,101 discloses a thin sheet of a soft, ductile, flexible material, such as aluminum, brass, plastic or the like, having a knurled pattern embossed to provide an improved gripping surface. The sheet can be applied to solid objects using an adhesive.
U.S. Pat. No. 4,488,918 discloses a plastic film having a non-slip surface comprising spaced, random patterns of rigid peaks and ridges formed of a second thermoplastic material co-extruded with and bonded to a plastic film. The surface has a pattern of relatively high, sharp, irregular plastic peaks and ridges, sufficiently sharp, hard and rough to effect a mechanical gripping with other surfaces.
U.S. Pat. No. 5,234,740 discloses a slip control surface with a structured surface. The structured surface includes an array of protrusions, typically triangular pyramids. The patent discloses that the sheeting may be applied to the handles of athletic equipment such as softball bats, golf clubs, tennis, racquetball, squash, badminton racquets, as well as the handles of tools.
The present invention relates to an improved friction control or gripping surface that has a pleasant and soft feel, high frictional properties and good gripping performance in both wet and dry conditions. The gripping surface is a soft micro-structured surface having an array of flexible upstanding stems of a variety of shapes produced from a thermoplastic elastomer. The size, spatial distribution, flexibility of the stems, stem array pattern, and the properties of the elastomer material all contribute to the soft feel of the surface, vibration dampening, and the gripping performance under wet and dry conditions. The various embodiments of the present friction or slip control surface may include micro-channels, an absorbent layer and hydrophilic/hydrophobic regions all for directing fluids away from the upstanding stems, leaving them dry and providing high frictional performance even in wet conditions. The present slip control article may be formed in a sheet structure, such as a wrap that can be applied to another article. Alternatively, the slip control article may be incorporated into a variety of molded or manufactured articles, including sport grips for golf clubs, baseball bats, racquets, bicycle handles, exercise equipment, household articles, construction and surgical tools, non-slip walking surfaces for swimming pool decks, diving boards, bathtubs.
In one embodiment, the slip control article comprises a backing layer having a first surface with an array of at least 15.5 stems/centimeter2 (100 stems per square inch), and more typically at least 54 stems/centimeter2 (350 stems per square inch) and a second surface. At least a portion of an exterior surface of the upstanding stems is an elastomeric material. The stems have an aspect ratio (stem height:stem diameter) of at least 1.25, and preferably at least 1.5, and more preferably at least 2.0 and most preferably greater than 3.0. The first surface has a static coefficient of friction when dry of at least 0.6 and a static coefficient of friction when wet within 20% of the static coefficient of friction when dry. Therefore, frictional properties do not substantially degrade when water is present. The first surface has a peel strength and a tensile strength of substantially zero when engaged with another slip control surface.
In one embodiment, an array of upstanding stems comprising an elastomeric material is also formed on the second surface. The second surface has a static coefficient of friction when dry of at least 0.6 and a static coefficient of friction when wet within 20% of the static coefficient of friction when dry. The second surface has a peel strength and a tensile strength of substantially zero when engaged with another slip control surface.
In other embodiments, the static coefficient of friction when dry is at least 1.0 or at least 2.0. The first surface has a dynamic shear strength of at least 23,268 dynes/centimeter2 (5.4 ounces/inch2), and preferably more than 43,090 dynes/centimeter2 (10 ounces/inch2), and more preferably at least 77,562 dynes/centimeter2 (18 ounces/inch2) and most preferably at least 107,725 dynes/centimeter2 (25 ounces/inch2) when engaged with another slip control surface at a pressure of about 53 grams/6.45 centimeter2. The high shear forces are due primarily to the frictional properties of the elastomeric materials, not a mechanical interlock of the stems, such as on a mechanical fastener.
The backing layer may be one or more layers, such as a reinforcing web, a foam layer, a substantially inelastic polymeric layer, or an adhesive or foamed adhesive layer, depending on the application of the slip control article. In one embodiment, the backing layer may be the elastomeric material integrally formed with the upstanding stems. The backing layer may be elastic or inelastic, thick or thin, porous or non-porous, with or without an adhesive layer, etc. In one embodiment, a non-elastomeric backing layer may form a portion of the upstanding stems. Since the backing layer may optionally be extremely thin, the present slip control article may be configured as a very thin wrap or gripping tape suitable for use as lightweight gripping applications. Alternatively, the backing layer may be a portion of a molded, extruded or manufactured article.